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IMU calculations: Preperations

1: Load the log files

Open the Ground Control Station, make sure the AutoQuad main widget is on the screen, and select ‘Generate Parameter.’

NOTE: If you are using a DIMU, remember to check the box ‘Use DIMU ‘:

Now select ‘Add Static ‘ and add your static log file(s) from the freezer calibration, then ‘Add Dynamic ‘ for the dynamic calibration log files.

2: Retrieve magnetic inclination for your location

The next step will require an estimate of your magnetic inclination for your geographic location.

Inclination is the amount of degrees a compass needle will point either upwards or downwards into the earth if the compass is rotated to a vertical orientation.

IMPORTANT NOTE: For mathematical reasons, AutoQuad has the inclination reversed. This is the opposite of what the online tools shows. You should always make sure that the define produced has the correct polarity:

  • In the northern hemisphere, inclination will always be negative (ex: -70.33)
  • In the southern hemisphere, inclination will always be positive  (ex: 70.33)


Please read the Magnetic Inclination and Declination page for more details about retrieving and setting up magnetic inclination and declination.

The declination and inclination for your location can be retrieved from the site http://magnetic-declination.com/

Find your location and click on the map:


Note that this tool shows inclination as degrees/minutes. AutoQuad operates with decimal degrees. The QGC groundstation can do the conversion:

In this example the inclination reported in the tool is 67 degrees and 6 minutes.

Since there are up to 60 mins per degree, when the minute value is in single digits, you have to enter a leading zero before the single digit minute value. So in this case that is 67.06

If you have a 2 digit minute count – Like: 70 degrees and 15 minutes, then you would just put in: 70.15

Enter this inclination number in the inclination in the first field and press ‘calc.’ The inclination is then reversed to negative polarity (a minus sign is added) and then converted to decimal degrees before a define is produced:

#define IMU_MAG_INCL -67.10

3: Create your parameters file.

All calculations should be saved to a file.  You can create a new param file by clicking on the ‘Create‘ button. Select a appropriate name for it and save it by selecting ‘ open.

Switch to the ‘All generated parameter’ tab. This window contains the contents of your param file, which should currently be empty.

Now select and copy (CTRL + C) the ‘#define IMU_MAG_INCL xx.xxxx’ you just created in the previous step, and  paste it (CTRL + V) into the blank part of this window. The result should look something like this:

Save your new parameter file by clicking the ‘save to para file’ button to the left of the window.

You are now ready for the actual calculations. Go to the next page to proceed.

This page was created on 18-Jun-12 by jussi. Last modified on 23-Aug-14 by jussi.